Aromatic Trifluoromethylation with Metal Complexes

Since the discovery of the McLoughlin-Thrower reaction in 1960s, considerable progress has been made in the important, demand-driven area of metal-promoted and metal-catalyzed aromatic trifluoromethylation. Important advancements have also been made in the development of Cu-catalyzed trifluoromethylations, and Ar-CF3 bond formation with well defined Cu(I) complexes. Although in some cases aryl bromides can be successfully used in Cu-mediated perfluoroalkylation reactions, iodoarenes are much more preferred due to their enhanced reactivity. Palladium is incomparably more costly than copper. Therefore, a utilizable nucleophilic aromatic trifluoromethylation process based on Pd must use catalytic, minimal quantities of this precious metal. Furthermore, many ligands employed in various Pd-catalyzed reactions often cost more than the metal itself. Another problem associated with the development of new ligands for Pd-catalyzed trifluoromethylation reactions is the facile transmetalation reaction.